I'd say Maisy, because she is a bulldozer
now if we were talking a fight between two dogs (not these two here) , i would place a VERY high wager on the lil jack russel.
we had a incident here in Vancouver, between a pitbull and a jack russell. The Jack russel was torn up pretty bad, half its back skin hanging off and multiple puncture wounds form the pitty. Yet that lil jack kept on blitzing the pit bull, darting in biting and tearing and darting out. finally won the fight by biting down and holding onto the pitties, "package". The pitty screamed and screamed (i was gpoing to say yelped but it was'nt a yelp). Jack russel bit down harder and tore off the bits.
i think they would make a good bear dog.